ios表单上传图片或文件

http://www.cocoachina.com/bbs/read.php?tid-89985-page-1.html

http://www.jianshu.com/p/44629e5bf986

http://www.jianshu.com/p/a0e3c77d3164

http://blog.csdn.net/u013252770/article/details/51463482